So gaining subscribers is really just a time thing. the best time to publish, I found is between 11am and 1pm, that way it is not too early in the morning that it gets lost in the fresh page, but not so late that people check the fresh page or their notifications and miss it.
I try to publish once or twice a week, but usually always on Mondays, just for consistency sake. I am not sure if a certain day of the week is better or worse to publish on. I just paid attention to when I usually got on to read stuff and did it around that time.
While sub for subs is a bad idea, chapter comment for chapter comment is a good one. If they like your book they might sub, and you at least get feedback from it.
Try and interact with people on the forums as much as possible. your name becomes more recognizable that way too
And comment back on your comments. The number of comments, likes, and views you get plays into the popular and trending categories.
And lastly, as I said earlier, it just takes time. Don't be afraid to post a thread on here asking for people to give you honest constructive criticism. Just asking them to read it will only get you so far. you want the constructive feedback.
And don't be afraid to ask questions.